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The prevalence of CF carriers (meaning they carry one mutation) is 1 in 25 in the Caucasian population. Most people don't even know that they are carriers until they have a child with CF. That means that the CF allele can unknowingly be passed down through generations. Carriers are typically asymptomatic and there is evidence to support that the CF mutation protected our ancestors from fatal diseases. So natural selection actually played a role in the proliferation of CF carriers.
What else can I help you with?
Does natural selection on single-gene trait cannot lead to changes in allele frequencies?
Natural selection acting on a single-gene trait can lead to changes in allele frequencies within a population. If individuals with a certain allele have a selective advantage, they are more likely to survive and reproduce, leading to an increase in the frequency of that allele in the population over time. This process is known as directional selection.
People with one sickle cell allele are not likely to get a malaria what is this an example of?
It is an example of Natural Selection, Modern Theories of Evolution.
What effect does natural selection have on the frequency of a recessive lethal allele?
Perhaps not much as the recessive allele is masked in heterozygous condition. Depends on penetration and expresivity of the lethal allele, but any homozygous expression is fatal, so one can expect negative frequency selection; the freqiency is kept low by selection.
What is natural selection and how does natural selection evolution?
A simplified explanation. Natural selection is the nonrandom survival and reproductive success of randomly varying organisms who by this reproductive success change the allele frequency over time in populations of organisms, which is evolution.
What must be true of a person with cystic fibrosis?
Both parents had at least one allele for cystic fibrosis.
What process would most likely act against any offspring with an allele for cataracts?
natural selection
Can you get Cystic fibrosis?
Cystic fibrosis is a genetic disease and can only be inherited through genes. It all depends on your parents alleles. Let's say that the allele for cystic fibrosis is c. If your Mum has the allele Cc it means she is hetrozygous. If you Dad has the same allele he is also hetrozygous. When they had children, the two small c's could come together to make a child with the alleles cc. (This means that the child has cystic fibrosis and has homozygous reccessive alleles.) When they had children their alleles could also come together to make CC (homozygous dominant- this means that person doesn't carry an allele for cystic firbrosis and will never get it. This means that if that person had children with another person who has the alleles CC, their child wouldn't get it), or it could make a child with Cc alleles. The child with Cc alleles wouldn't get cystic fibrosis because the allele big C (dominant allele) over powers the allele small c (reccessive- the cystic fibrosis allele). Although this person doesn't have cystic fibrosis their children might because they carry the allele for cystic fibrosis, which is c.
How is the sickle allele maintained through natural selection?
Heterozygous individuals pass the dominant and recessive alleles to offspring.
Which is more likely to be true natural selection or evolution?
Evolution, of course. Evolution can happen without natural selection in some cases; drift, flow. Generally though, natural selection causes evolution and then, by definition, would come first.
What is direct selection?
Directional selection is when natural selection favors a single phenotype. It occurs when there is a shift in population towards an extreme version of a beneficial trait.
How does environmental pressure affect natural selection?
When nothing happens to exert strong population pressure on that population, natural selection favors the allele frequency already present. When mutations cause new traits, natural selection weeds these traits out because they're not as efficient as the others.
The allele for cystic fibrosis is recessive. What does this mean?
The recessive nature of the cystic fibrosis allele means that an individual must inherit two copies of the allele (one from each parent) to express the condition. If a person has only one copy of the cystic fibrosis allele and one normal allele, they will be a carrier but will not exhibit symptoms of the disease. This inheritance pattern affects how the disease is passed on in families, with carriers having a 25% chance of having an affected child if both parents are carriers.
